Interestingly, the metro system here in Valencia, Spain is a true metro system by Wikipedia's own definition, but doesn't make the list. I presume the reason is that the metro, light railway and tram lines are operated together as a kind of integrated system.

This seems to be missing quite a few cities. I know for a fact that many more german cities, such as Cologne, Bonn, Dusseldorf, Suttgart, Frankfurt and the whole Ruhr area have a well-functioning Metro System, above ground and below.

Frankfurt definitely has a metro system, and it's not a "light metro" either. It is of course possible that Wikipedia lists only cities whose metro stations are mostly underground. However, that would seem to rule out Oslo and no doubt others as well.

The reason Frankfurt is not included is beacuse the network is not fully grade separated, above or underground does not matter. Again, the difference with rapid transit oftentimes is debatable and sometimes arbitrary.

Absolutely no idea how Frankfurt's isn't considered a metro. Only thing I can guess is they ding it for integrating with the suburban lines that definitely are light rails. That being said there are at least 86 true Ubahn stations.

St Petersburg in general is, in my opinion, the most beautiful city in Europe. Beating out Paris, Amsterdam, Copenhagen, Stockholm, Rome, Odessa, Athens, Salzburg, Venice, San Marino, Kiev, Tallinn, Helsinki, Oslo, Moscow, Prague, Budapest and the others I've been to, anyway. I've never been to Spain or Switzerland. Moscow also has a beautiful metro.

The correct spelling is Kyiv, and it is in Europe. Istanbul is commonly accepted as being on the European continent. Yekaterinburg however, is geographically in Asia. If we use your logic then every city in Russia doesn't count because by your logic Eastern Europe isn't really Europe...this is why they teach geography in school kids!

Why is the date for London showing as 1890? It first opened in 1863 with steam traction and was electrified in 1890 but it was still a metro system from day 1, with the first line being known as the "Metropolitan Railway". The referenced wiki article implies that too. In 2013 it made a big celebration of being 150 years old, see "The London Underground celebrates 150 years".

While Newcastle itself is not so big, the Newcastle metropolitan area (Tyneside) is also one of the largest in the UK. Furthermore, Manchester and Birmingham already have extensive light rail/tram systems, and the West Yorkshire commuter rail network, which includes Leeds as well as other cities like Bradford and Wakefield, and also Liverpool's Merseyrail, do the same job as a metro. So I suppose it's less a case of Newcastle being prioritised, but rather they chose a different system (metro as opposed to light rail/commuter trains.)

Dnipro's metro is probably the funniest one on this list. The Soviets planned a full metro for this pretty big Ukrainian city (over 1m residents) in the 1980s, but the USSR broke apart right after construction had started, and the Ukrainian government just opened it up after they finished what they could with limited resources. Six stops barely covering half the city center. I rode it one time to just say that I did, and there was hardly anyone on it and hardly anything to go to at each stop.